In the satellite communications and telemetry field it is desirable to have tracking antennas that are inexpensive to construct and that are virtually maintenance free. To permit changes in its orientation, an antenna reflector must be able to pivot about one or more axes, depending on the type of mounting used.
One type of mounting structure is the elevation over azimuth type in which structures must provide for independent rotation about the horizontal or elevation axis and also about the vertical or azimuth axis. Previous structures have utilized different drive assemblies to provide the rotational power to achieve the proper elevation and azimuth orientations. Such drive assemblies are more expensive to design, manufacture and maintain. Therefore, there has existed a need for a modular drive assembly that can be used in either the elevation or azimuth orientation.
Typically, drive assemblies have a central hollow portion for wiring and cable associated with the antenna reflector. In designing the drive assembly it is advantageous to shield the central portion from RFI/EMI radiation. Unshielded, the RFI/EMI radiation interferes with the electrical signals in the wiring and cable located in the central hollow portion of the drive assembly.
With a modular drive assembly design, it is undesirable to have additional weight and space allotted for RFI/EMI shielding. There exists a need for an effective compact or integral RFI/EMI shield. In addition to shielding the assembly from RFI/EMI radiation, it is desirable to design the pedestal assembly to require little or no maintenance. One way to eliminate potential problems is to keep any moisture or dirt from getting into the assembly. Moisture can cause corrosion or loss of lubricant and can detrimentally effect the electrical system. Dirt particles in the assembly can interfere with the operation of the gears and bearings and can cause premature wearing of the assembly. Thus, there exists a need for an effective and integral method of keeping dirt and moisture out of a modular drive unit assembly.
In the past, drive assemblies for mounting antenna reflectors were not modular in design. In addition, the drive assemblies were larger in size and weight because the turntable was designed to directly bear the load attached to it. Thus, there exists a need for a smaller, lighter weight drive assembly design where the attached load is more effectively distributed.